Asfarviridae
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As Asfarviridae refers to a family of viruses whose members primarily infect pigs and African swine fever cause. There is only one genus in the family : Asfivirus (ASFV). The name of this virus is an acronym: A frican s wine f ever a nd r elated viruses. So far only one species has been identified. These viruses are the only DNA viruses transmitted by arthropods . The viruses all have a virus envelope , have a dsDNA (double-stranded DNA ) and are attached to the phylum of the Nucleocytoviricota (outdated Nucleocytoplasmic large DNA viruses , NCLDV; earlier proposals had been " Nucleocytoplasmaviricota " or - in the rank of order - " Megavirals ") added. The Asfivirus shows similarities with the Poxviridae and the Phycodnaviridae in the genome structure and the replication strategies , but has a virion structure different from the Poxviridae and some other properties that distinguish it from the latter. For this reason, the Poxviridae (with their order Chitovirales ) and the Asfarviridae (with their order Asfuvirales ) were placed in the joint, newly created class Pokkesviricetes by the International Committee on Taxonomy of Viruses (ICTV) in March 2020 .
Structure and genome
The virion consists of a shell, a capsid , a core and the nucleoprotein complex . These are spherical and their diameter is between 175 and 215 nm. The capsid is icosahedral ( T = 189-217) with a diameter of 172-191 nm. The capsomer has a diameter of 13 nm and 1892 to 2172 of them form a capsid . The genome of the virus is a linear, double-stranded DNA (ds-DNA) with a length of 170 and 190 kb . Their GC content is 39%.
Multiplication and Host
The virus can be grown in cell cultures without cell changes becoming visible under the light microscope. In tissue biopsies one can see intracytoplasmic acidophilic inclusion bodies , which correspond to the viroplasm . The viruses replicate cytoplasmic and the virions mature by budding from plasma membranes. The viruses in this family infect domestic pigs and their relatives. The natural hosts of the virus are warthogs ( Phacochoerus africanus ) and river pigs ( Potamochoerus porcus ), the virus being transmitted as a vector by leather ticks . Infected young warthogs develop pronounced viraemia and infect the ticks when they eat blood. Old warthogs are often already immune due to their high prevalence . The virus can multiply in the ticks, where it is also transmitted to the following generation without a blood meal (vertical, transovarian transmission). Horizontal transmission between adult ticks during sexual intercourse has been described.
During infection, the virus can reproduce in the host in erythrocytes , endothelial cells, and leukocytes , but not in epithelia . Accordingly, the virus can be obtained from the blood, spleen tissue, lymph nodes and tonsils of infected animals. None of the virus species infects humans.
Epidemiology
The occurrence of this virus family was originally limited to Africa. However, the virus has recently spread to southern Europe and America.
Systematics
Schulz et al suggest the following system:
| Nucleocytoviricota (NCLDV): Pokkesviricetes |
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Koonin et al. (2015 and 2019) propose an internal system of the NCLDV in which the (extended) family of Asfarviridae form a sister group of Poxviridae . Together they then form a 3rd branch ( English branch ) of the NCLDV, next to a 1st branch with Mimiviridae and Phycodnaviridae , and a 2nd branch with the Pithoviridae , Marseilleviridae and Iridoviridae . The ICTV followed this suggestion with its Master Species List (MSL) # 35 in March 2020, even though Rolland et al. (2019) saw the Pokkesviricetes within the NCLDV closer to the extended family of Mimivirdae (i.e. the order Imitervirales ).
Dinodnavirus has been proposed as a further member of this extended Asfarviridae group .
Individual evidence
- ↑ a b c d e f g ICTV: ICTV Taxonomy history: African swine fever virus , EC 51, Berlin, Germany, July 2019; Email ratification March 2020 (MSL # 35)
- ^ Index of Viruses - Asfarviridae (2006). In: ICTVdB - The Universal Virus Database, version 4. Büchen-Osmond, C (Ed), Columbia University, New York, USA. http://www.ncbi.nlm.nih.gov/ICTVdb/Ictv/fs_index.htm
- ↑ Frederik Schulz, Lauren Alteio, Danielle Goudeau, Elizabeth M. Ryan, Feiqiao B. Yu, Rex R. Malmstrom, Jeffrey Blanchard, Tanja Woyke: Hidden diversity of soil giant viruses , in: Nature Communicationsvolume 9, Article number: 4881 (2018 ) from November 19, 2018, doi: 10.1038 / s41467-018-07335-2
- ↑ Eugene V. Koonin, Natalya Yutin: Evolution of the Large Nucleocytoplasmatic DNA Viruses of Eukaryotes and Convergent Origins of Viral Gigantism , in: Advances in Virus research, Volume 103, AP January 21, 2019, doi: 10.1016 / bs.aivir.2018.09 .002 , pp. 167-202. The toilet viruses are partially missed as toilet viruses.
- ↑ Clara Rolland, Julien Andreani, Amina Cherif Louazani, Sarah Aherfi, Rania Francis, Rodrigo Rodrigues, Ludmila Santos Silva, Dehia Sahmi, Said Mougari, Nisrine Chelkha, Meriem Bekliz, Lorena Silva, Felipe Assis, Fábio Dornas, Jacques Yaacoub Bou Khalil, Isabelle Pagnier, Christelle Desnues, Anthony Levasseur, Philippe Colson, Jônatas Abrahão, Bernard La Scola: Discovery and Further Studies on Giant Viruses at the IHU Mediterranee Infection That Modified the Perception of the Virosphere , in: Viruses 11 (4), March / April 2019, pii: E312, doi: 10.3390 / v11040312 , PMC 6520786 (free full text), PMID 30935049 , Fig. 2a
- ↑ H. Ogata, K. Toyoda, Y. Tomaru, N. Nakayama, Y. Shirai, JM Claverie, K. Nagasaki: Remarkable sequence similarity between the dinoflagellate-infecting marine girus and the terrestrial pathogen African swine fever virus. In: Virol J. 6, 2009, p. 178.
Web links
- MeSH Asfarviridae
- dsDNA Viruses> Asfarviridae ICTV Report from March 2018
- Viral zone : Asfarviridae